The longest-running scientific experiment in the world is the Pitch Drop that began in Queensland, Australia, in 1927. The setup is basically putting pitch in a funnel and see if it drips out. The point is to prove that pitch is a viscous liquid that will flow, instead of a solid. The problem is that it takes years for a drop to actually drop, and has never been witnessed. Read more about the history of the experiment here. A similar experiment has been running since 1944 in Scotland, and a drop was videotaped for the first time last year. Now, the ninth drop of the Queenland University Pitch Drop has made its way down.

This video is a time lapse of the past two years of the Pitch Drop experiment. The ninth drop has now collided with the eighth drop! However, it has yet to separate from the pitch above it. You can watch the progress of the pitch drop live on a very boring webcam. You can also sign up to be notified in case anything happens. -via Digg

'...The longest-running scientific experiment in the world is the Pitch Drop ...'Extraordinary claims require extraordinary evidence. I think there are numerous longer running scientific experiments than the Pitch Drop experiment...-Beverly Clock-Oxford Bell- Agriculture-The Scientific Method itself-Capitalism-Non-person legal entities-Selective breeding of different species, I guess that could just be 'domestication'. ..Even if you add in the caveat used by the Guinness World Record people, 'continuous', I don't think that really clears it up. Many of the previous list span a greater time without interruption. Also, who is to say the pitch didn't stop flowing momentarily? This is after all an experiment to better understand the way it moves and it doesn't sound as if there is high speed video equipment monitoring it.